(1) Field of the Invention
The present invention refers to a device for the treatment of flat materials, more particularly for embossing and/or satinizing foils, the device comprising at least three embossing rolls.
(2) Related Art
A device of this kind is e.g. known from WO-A-00/69622, this reference being exclusively referring to rolls having each the same structure, more particularly truncated pyramidal teeth where each tooth of a roll engages between four teeth of another roll while the additional roll has the function of providing an increased embossing quality and a reduced wear of the rolls especially in the case of flat materials having a large paper and small metallized proportion.
The embossing station for embossing fiber webs as for handkerchiefs or toilet paper according to EP-A-1 074 381 comprises a smooth mating roll and two embossing rolls disposed above the latter in a V-shaped arrangement. However, such an arrangement is unsuitable for satinizing or for embossing special signs on materials such as cigarette paper as the embossing rolls, which are not described in detail and are illustrated with a relatively coarse profile, are not intended for this purpose.
EP-A-498 623 discloses the application of pairs of steel and rubber rolls with knobs on the steel rolls that fit into corresponding recesses in the rubber roll. The application of two pairs of identical or similar rolls is also disclosed. Such pairs of rolls with recesses in a rubber roll are unsuitable for a precise fine embossing and satinizing as it is required e.g. for the treatment of packaging foils where the flat material is a fibrous material such as paper which is bulked after the treatment.
U.S. Pat. No. 4,280,978 discloses an embossing and perforating device including an embossing and two mating rolls, the mating rolls comprising recesses that are adapted to the spikes of the embossing rolls. This device is also unsuitable for a precise fine embossing and satinizing.
U.S. Pat. No. 2,290,608 discloses a method and device for wrinkling a metal foil, thereby producing irregular patterns that are suitable for reflectors. The metal foil passes between two rolls provided with pegs, longitudinal grooves, wave-shaped grooves, or honeycomb structures and is rotated by 90° or 45° after each pass. A device of this kind is neither appropriate for embossing nor for satinizing, and it is also inappropriate for embossing security features on suitable materials.
Further known are U.S. Pat. No. 5,007,271 or U.S. Pat. No. 5,598,774 to the applicant of the present invention, which disclose embossing devices with two embossing rolls for flat materials. In particular, the flat materials in question are bands or strips one face of which is coated with metal, generally with aluminum, and whose support consists of paper or another fibrous material, or foils, e.g. of synthetic materials, of metal, or of compound materials.
Inter alia, the latter embossing devices are used in the packaging industry for the purpose of satinizing packaging materials while seals, emblems and the like may be stamped at the same time. In this context, satinizing means providing the surface with a fine pattern in the millimeter and submillimeter range. Strip or sheet packaging materials of this kind, also called innerliners, are e.g. used for packaging tobacco products, cigarettes, foods, chocolates, chewing gums and the like.
According to the cited reference U.S. Pat. No. 5,598,774, the driven roll is supported stationarily while at least one of the two mating rolls is free-wheeling and journalled such that the axes of the embossing rolls are capable of an excursion both in the longitudinal and/or in the contact pressure direction and/or in the travelling direction of the material. This allows an adjustment of the rolls that provides a precise mutual engagement of the teeth and thus a perfect processing of the material without the risk of wrinkling it.
The last mentioned devices have been successful and still are as long as the satin-finished foils, more particularly packaging foils, are mainly composed of aluminum or mainly of easily foldable paper. In the manufacture of cigarette packages, for example, these packaging materials serve the purpose of wrapping up a counted number of cigarettes in the production process in order to be subsequently inserted in a box.
Whereas the first mentioned device according to WO-A-00/69622 provided the expected advantages in the embossing of flat materials that are difficult to emboss otherwise, it has appeared that the rolls do not have suitable surface structures for embossing certain special signs on the flat material that produce optical effects depending on the viewing position and/or the light source.